The invention relates to prosthetic heart valves. More particularly, the invention relates to prosthetic heart valves for the replacement of damaged mitral or tricuspid heart valves.
Heart valve insufficiency can be a debilitating and possibly life threatening condition. For example, heart valve regurgitation, i.e., backward leakage of blood at a heart valve, results in reduced pumping efficiency. With respect to mitral valve regurgitation, compensatory mechanisms such as hypertrophy and dilation of the ventricle suggest early treatment to prevent progressive deterioration of ventricular function. Diagnosis of mitral regurgitation can be performed using visualization with transesophageal echocardiography or by echocardiography. In particular, defective leaflet coaptation and the site and direction of the regurgitant flow can be examined to evaluate likely modes of failure.
Mitral valve prolapse, i.e., myxomatous degeneration of mitral valve leaflets, is the most common cause of mitral regurgitation in North America. Rheumatic heart disease was the most common cause of mitral regurgitation in the United States thirty years ago and is still the most common cause of mitral regurgitation in developing countries. Chronic rheumatic heart disease results in retraction, deformity and rigidity of one or both mitral valve cusps as well as structural abnormalities in the commissures, chordae tendineae and papillary muscles. Ischemic mitral regurgitation (IMR), i.e., anemia of the valve tissue due to reduced arterial blood flow feeding the valve tissue, is the second most common cause of mitral valve regurgitation. Studies suggest that annular irregularities and posterior papillary muscle fibrosis with scarring of the underlying ventricular wall may be associated with IMR.
Many cases of mitral regurgitation can be repaired by modifications of the original valve in a procedure generally referred to as valvuloplasty. For example, one repair technique uses an annuloplasty ring to provide structural support to the natural annulus of the native valve. For severe cases of heart valve damage, however, reconstructive valvular surgery may not be possible. In such cases, valve replacement may be required.
Physicians use a variety of prostheses to correct problems associated with the cardiovascular system, especially the heart. For example, the ability to replace or repair diseased heart valves with prosthetic devices has provided surgeons with a method of treating heart valve deficiencies due to disease and congenital defects. A typical procedure involves removal of the native valve and surgical replacement with a prosthetic heart valve.
Both mechanical heart valve prostheses and tissue based heart valve bioprostheses have been used to replace damaged heart valves. Mechanical heart valves have the advantage of better durability, but patients with mechanical heart valves generally are required to use anticoagulants throughout their lifetimes. Anticoagulants have associated risks, such as hemorrhages, embolism and thromboembolism. Tissue based bioprostheses do not require the long term use of anticoagulants due to a lower incidence of thromboembolism.